The HD 3450 doesn't have a whole lot going for it. It would be okay for a home theater PC thanks to hardware decoding, but that's about all. These days with the price of motherboards and their integrated graphics you don't even need a card like this for an office machine.
You really have to wonder what the market is like for these low-end cards these days due to that reason alone. Even in the event that you wanted a video card for a HTPC, we would probably opt for something better that had HDMI unless you really needed the low profile ability.
The HD 3650 on the other hand is your typical mid-range graphics card. It's going to play most games at 1024 x 768 and 1280 x 1024. Once you go any higher than that though, you're going to start running into problems with your frame rate.
Thanks to the inclusion of the HDMI adapter in the HD 3650, it doesn't make it a bad choice for HTPC users, especially since you could do a bit of low res big screen gaming if you wanted to.
The HD 3650 has a market we can easily see is useful, but we really have to wonder what kind of person buys the HD 3450 as it honestly seems that the market would be taken up with integrated graphics these days.
Sapphire HD 3450
Sapphire HD 3650